As part of an expanding programme of battlefield automation, the American air force has said it is now training more drone operators than fighter and bomber pilots.

In a controversial shift in military thinking – one encouraged by the confirmed death of Pakistani Taliban leader Baitullah Mehsud in a drone-strike on 5 August – the air force is looking to hugely expand its fleet of unmanned aircraft by 2047.

Three years ago, the service was able to fly just 12 drones at a time; now it can fly more than 50. At a trade conference outside Washington last week, military contractors presented a future vision in which pilotless drones serve as fighters, bombers and transports, even automatic mini-drones which attack in swarms.

Five thousand robotic vehicles and drones are deployed in Iraq and Afghanistan. By 2015, the Pentagon’s $230bn (£140bn) arms procurement programme Future Combat Systems expects 15% of America’s armed forces to be robotic.

A recent study ‘The Unmanned Aircraft System Flight Plan 2020-2047’ predicted a boom in drone funding to $55bn by 2020 with the greatest changes coming in the 2040s.

“The capability provided by the unmanned aircraft is game-changing,” said General Norton Schwartz, the air force chief of staff. “We can have eyes 24/7 on our adversaries.”

An international debate is needed on the use of autonomous military robots, a leading academic has said. Noel Sharkey of the University of Sheffield said that a push toward more robotic technology used in warfare would put civilian life at grave risk.

Technology capable of distinguishing friend from foe reliably was at least 50 years away, he added. However, he said that for the first time, US forces mentioned resolving such ethical concerns in their plans.

“Robots that can decide where to kill, who to kill and when to kill is high on all the military agendas,” Professor Sharkey said at a meeting in London. “The problem is that this is all based on artificial intelligence, and the military have a strange view of artificial intelligence based on science fiction.”

Professor Sharkey, a professor of artificial intelligence and robotics, has long drawn attention to the psychological distance from the horrors of war that is maintained by operators who pilot unmanned aerial vehicles (UAVs), often from thousands of miles away.

“These guys who are driving them sit there all day… they go home and eat dinner with their families at night,” he said. “It’s kind of a very odd way of fighting a war – it’s changing the character of war dramatically.”